Add support for ipn-scheme to BIBE CLA
This MR makes the BIBE CLA run properly on nodes with the ipn-scheme.
Before, the agent needed for the communication between lower and upper layer always registered with the id "bibe", which does not comply with the ipn-scheme.
Now the agent checks the EID-scheme of the partner node and registers either with "bibe", for the dtn-scheme, or 2925 for ipn.
Closes #89 (closed)